1/*
  2** $Id: lgc.h $
  3** Garbage Collector
  4** See Copyright Notice in lua.h
  5*/
  6
  7#ifndef lgc_h
  8#define lgc_h
  9
 10
 11#include "lobject.h"
 12#include "lstate.h"
 13
 14/*
 15** Collectable objects may have one of three colors: white, which means
 16** the object is not marked; gray, which means the object is marked, but
 17** its references may be not marked; and black, which means that the
 18** object and all its references are marked.  The main invariant of the
 19** garbage collector, while marking objects, is that a black object can
 20** never point to a white one. Moreover, any gray object must be in a
 21** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
 22** can be visited again before finishing the collection cycle. (Open
 23** upvalues are an exception to this rule.)  These lists have no meaning
 24** when the invariant is not being enforced (e.g., sweep phase).
 25*/
 26
 27
 28/*
 29** Possible states of the Garbage Collector
 30*/
 31#define GCSpropagate	0
 32#define GCSenteratomic	1
 33#define GCSatomic	2
 34#define GCSswpallgc	3
 35#define GCSswpfinobj	4
 36#define GCSswptobefnz	5
 37#define GCSswpend	6
 38#define GCScallfin	7
 39#define GCSpause	8
 40
 41
 42#define issweepphase(g)  \
 43	(GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
 44
 45
 46/*
 47** macro to tell when main invariant (white objects cannot point to black
 48** ones) must be kept. During a collection, the sweep
 49** phase may break the invariant, as objects turned white may point to
 50** still-black objects. The invariant is restored when sweep ends and
 51** all objects are white again.
 52*/
 53
 54#define keepinvariant(g)	((g)->gcstate <= GCSatomic)
 55
 56
 57/*
 58** some useful bit tricks
 59*/
 60#define resetbits(x,m)		((x) &= cast_byte(~(m)))
 61#define setbits(x,m)		((x) |= (m))
 62#define testbits(x,m)		((x) & (m))
 63#define bitmask(b)		(1<<(b))
 64#define bit2mask(b1,b2)		(bitmask(b1) | bitmask(b2))
 65#define l_setbit(x,b)		setbits(x, bitmask(b))
 66#define resetbit(x,b)		resetbits(x, bitmask(b))
 67#define testbit(x,b)		testbits(x, bitmask(b))
 68
 69
 70/*
 71** Layout for bit use in 'marked' field. First three bits are
 72** used for object "age" in generational mode. Last bit is used
 73** by tests.
 74*/
 75#define WHITE0BIT	3  /* object is white (type 0) */
 76#define WHITE1BIT	4  /* object is white (type 1) */
 77#define BLACKBIT	5  /* object is black */
 78#define FINALIZEDBIT	6  /* object has been marked for finalization */
 79
 80#define TESTBIT		7
 81
 82
 83
 84#define WHITEBITS	bit2mask(WHITE0BIT, WHITE1BIT)
 85
 86
 87#define iswhite(x)      testbits((x)->marked, WHITEBITS)
 88#define isblack(x)      testbit((x)->marked, BLACKBIT)
 89#define isgray(x)  /* neither white nor black */  \
 90	(!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
 91
 92#define tofinalize(x)	testbit((x)->marked, FINALIZEDBIT)
 93
 94#define otherwhite(g)	((g)->currentwhite ^ WHITEBITS)
 95#define isdeadm(ow,m)	((m) & (ow))
 96#define isdead(g,v)	isdeadm(otherwhite(g), (v)->marked)
 97
 98#define changewhite(x)	((x)->marked ^= WHITEBITS)
 99#define nw2black(x)  \
100	check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
101
102#define luaC_white(g)	cast_byte((g)->currentwhite & WHITEBITS)
103
104
105/* object age in generational mode */
106#define G_NEW		0	/* created in current cycle */
107#define G_SURVIVAL	1	/* created in previous cycle */
108#define G_OLD0		2	/* marked old by frw. barrier in this cycle */
109#define G_OLD1		3	/* first full cycle as old */
110#define G_OLD		4	/* really old object (not to be visited) */
111#define G_TOUCHED1	5	/* old object touched this cycle */
112#define G_TOUCHED2	6	/* old object touched in previous cycle */
113
114#define AGEBITS		7  /* all age bits (111) */
115
116#define getage(o)	((o)->marked & AGEBITS)
117#define setage(o,a)  ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
118#define isold(o)	(getage(o) > G_SURVIVAL)
119
120#define changeage(o,f,t)  \
121	check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))
122
123
124/* Default Values for GC parameters */
125#define LUAI_GENMAJORMUL         100
126#define LUAI_GENMINORMUL         20
127
128/* wait memory to double before starting new cycle */
129#define LUAI_GCPAUSE    200
130
131/*
132** some gc parameters are stored divided by 4 to allow a maximum value
133** up to 1023 in a 'lu_byte'.
134*/
135#define getgcparam(p)	((p) * 4)
136#define setgcparam(p,v)	((p) = (v) / 4)
137
138#define LUAI_GCMUL      100
139
140/* how much to allocate before next GC step (log2) */
141#define LUAI_GCSTEPSIZE 13      /* 8 KB */
142
143
144/*
145** Check whether the declared GC mode is generational. While in
146** generational mode, the collector can go temporarily to incremental
147** mode to improve performance. This is signaled by 'g->lastatomic != 0'.
148*/
149#define isdecGCmodegen(g)	(g->gckind == KGC_GEN || g->lastatomic != 0)
150
151
152/*
153** Control when GC is running:
154*/
155#define GCSTPUSR	1  /* bit true when GC stopped by user */
156#define GCSTPGC		2  /* bit true when GC stopped by itself */
157#define GCSTPCLS	4  /* bit true when closing Lua state */
158#define gcrunning(g)	((g)->gcstp == 0)
159
160
161/*
162** Does one step of collection when debt becomes positive. 'pre'/'pos'
163** allows some adjustments to be done only when needed. macro
164** 'condchangemem' is used only for heavy tests (forcing a full
165** GC cycle on every opportunity)
166*/
167#define luaC_condGC(L,pre,pos) \
168	{ if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
169	  condchangemem(L,pre,pos); }
170
171/* more often than not, 'pre'/'pos' are empty */
172#define luaC_checkGC(L)		luaC_condGC(L,(void)0,(void)0)
173
174
175#define luaC_objbarrier(L,p,o) (  \
176	(isblack(p) && iswhite(o)) ? \
177	luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
178
179#define luaC_barrier(L,p,v) (  \
180	iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0))
181
182#define luaC_objbarrierback(L,p,o) (  \
183	(isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0))
184
185#define luaC_barrierback(L,p,v) (  \
186	iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : cast_void(0))
187
188LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
189LUAI_FUNC void luaC_freeallobjects (lua_State *L);
190LUAI_FUNC void luaC_step (lua_State *L);
191LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
192LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
193LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
194LUAI_FUNC GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz,
195                                                 size_t offset);
196LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
197LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
198LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
199LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
200
201
202#endif